1. Field of the Invention
The present invention relates to a ratchet-type lever mechanism for seat lifter (or seat height adjuster), which is operable by rotation of an operation lever to actuate the seat lifter for the height adjustment of seat. Particularly, the invention is directed to a ratchet-type lever drive mechanism having a ratchet gear system provided about the shaft of a brake unit operatively connected with a seat lifter, wherein an operating lever can be rotated to cause the brake unit shaft to rotate in a desired direction corresponding to the direction in which the seat lifer is raised or lowered.
2. Description of Prior Art
A seat height adjuster or what is known as a seat lifter is incorporated in automotive seat to enable an occupant on the seat to selectively adjust the height of seat according to his or her physique and seating posture. In the seat lifter, typically known is a linkage-type seat lifter having forward and rearward links which are interlockingly movable and pivotally coupled with the forward and rearward portions of the seat, respectively, so that the seat may be raised and lowered via those two links. This seat lifter includes plural transmission gears (reduction gears and the like), a brake-unit, and a drive mechanism provided with a lever or handle, wherein the drive mechanism is operatively connected through the transmission gears and bake unit to the forward and rearward links. As known in the art, the brake unit provides a braking action on the drive mechanism to normally lock the links to a given position. Conventionally, the drive mechanism is provided with a dial-type rotary handle which is directly connected with a shaft of the brake unit. However, since a great load is applied to the seat lifter and the brake unit, it is highly possible that a user will use quite more force than normally required to rotate such dial-type handle with his and her one hand. In view of such problem, for instance, a ratchet-type lever drive mechanism is disclosed in the Japanese Laid-Open Patent Publication No. 2000-255295. According thereto, instead of the dial handle, an operating lever is used, which is connected with two ratchet pawl gears, and two ratchet wheel gears are fixed to the output shaft of the brake unit, such that, by vertical rotation of the operating lever, one of the two pawl gears may be selectively meshed with a corresponding one of the two ratchet wheel gears, thereby causing upward and downward motions of the seat lifter to raise and lower a seat to a desired level.
FIG. 1 a typical example of seat lifter (SL) provided with a conventional ratchet-type lever mechanism (110) similar to the foregoing mechanism. As is known, the seat lifter (SL), although only its one lateral side portion is shown, basically comprises a pair of forward link (80) and backward link (81), and a sector gear (84) pivotally connected via a connecting link (83) with the backward link (81). The forward link (80), facing to a side (F) forwardly of the seat lifter and seat cushion frame (F), is pivotally connected at its upper end with the seat cushion frame (F) via a pin (80a) and likewise connected at its lower end with a base frame or an upper rail of slide rail device (designated by (90)) via a pin (80b). The backward link (81), facing to a side (B) backwardly of the seat lifter (SL) and seat cushion frame (F), is at its midway part pivoted to the seat cushion frame (F) via pin (81a), while being pivotally connected at its lower end with the base frame or upper rail (at 90) via a pin (81b). The sector gear (84) is rotatably connected to the seat cushion frame (F). In the shown mode, an inwardly toothed gear portion (84a) is formed in the sector gear (84). Sector gear (84) is rotatably fixed to the seat cushion frame (F). On the other hand, the ratchet-type lever mechanism (110) includes a pair of first and second ratchet wheel gears (12u)(12d) fixed to the shaft of brake unit (16), and a bifurcated ratchet gear (300) connected with an operating lever (214). Though not shown, the first ratchet wheel gear (12u) has a known one-way clutch built therein, by which the gear (12u) itself is only permitted to rotate together with the shaft (16a) of brake unit (16) in clockwise direction to cause upward motion of the seat lifer (SL) to raise the seat cushion frame (F), while being free to rotate about the brake unit shaft (16a) in anticlockwise direction. On the other hand, the second ratchet wheel gear (12d) has another one-way clutch therein for only permitting the gear (12d) itself together with the brake unit shaft (16a) to rotate in anticlockwise direction to cause downward motion of the seat lifter (SL) to lower the seat cushion frame (F), while being free to rotate about the brake unit shaft (16a) in clockwise direction. The bifurcated ratchet gear element (300) is formed with a first pawl gear (300a) and a second pawl gear (300b), wherein the first pawl gear (300a) is bent and offset from the second pawl gear (300b). As s shown, the bifurcated ratchet gear (300) is securely supported on a bearing shaft (228) connected with the operating lever (214) and normally positioned at a point where both first and second pawl gears (300a)(300b) are out of mesh with the respective first and second ratchet wheel gears (12u)(12d).
As found in the foregoing conventional combination of ratchet-type lever mechanism (110) and seat lifter (SL), it has been customary that upward rotation of the operating lever (214) results in likewise upward movement of seat cushion frame (F) or a seat via the seat lifter (SL) for the sake of easiness in operation. Otherwise stated, in the seat lifter (SL), the backward link (81), the sector gear (84) and the connecting link (83) establish a particular transmission mechanism through which a normal upward rotation of operating lever (214) by a user or seat occupant is transmitted to both two links (80) (81), thereby transforming the rotation into upward motion of the seat lifter (SL) itself to raise a vehicle seat (not shown). Specifically, when a user rotates the lever (214) upwardly as indicated by the one-dot-chain arrow, the bifurcated ratchet gear (300) is rotated anticlockwise, bringing the first pawl gear toothed portion (226u) to mesh with the first ratchet gear wheel (12u). Then, as indicated by the arrows, both first ratchet gear wheel (12u) and shaft (16a) of brake unit (16) are rotated clockwise to cause simultaneous clockwise rotation of pinion gear (7) meshed with the inwardly toothed portion (84a) of sector gear (84), which in turn causes the likewise clock rotation of the sector gear (84).
Such clockwise rotation causes upward rotation of both two links (80) to raise the seat cushion frame (F) or not-shown seat. Therefore, this particular transmission mechanism of seat lifter (SL) naturally requires clockwise rotation as xe2x80x9cnormal direction of rotationxe2x80x9d for upward motion to raise a vehicle seat, as indicated by the arrow (N) in particular.
In contrast to such normal-rotation-type lever mechanism (110), there has been known a reverse-rotation-type seat lifter having a particular transmission mechanism requiring anticlockwise rotation as a xe2x80x9creverse direction of rotationxe2x80x9d to raise the vehicle seat. This is shown in FIG. 2, by way of one example, as designated by (SLxe2x80x2), which is basically identical to the afore-said seat lifter (SL), only excepting a sector gear arrangement (85) including an outwardly toothed gear (85a) and an integral backward link portion (85c). In other words, the transmission mechanism of this seat lifter (SLxe2x80x2) is formed by such combination of outwardly-toothed gear teeth (85a) and backward link portion (85c). Specifically, according to this reverse-rotation-type seat lifter (SLxe2x80x2), the sector gear arrangement (85) is pivotally secured by a pin (85b) to the seat cushion frame (F), while being at its integral backward link portion (85c) pivotally connected with the base member (90). Meshed with the outwardly-toothed gear teeth (85a) is the pinion gear (7) of the brake unit (16). Due to this particular structure, the shaft (16a) of brake unit (16) must be rotated anticlockwise, as indicated by the arrow (R), in order to raise the seat cushion frame (F).
However, when applying the foregoing known ratchet-type lever mechanism (110) to such reverse-rotation-type seat lifter structure (SLxe2x80x2) or other similar seat lifters having a mechanism requiring a reverse rotation to a normal rotation of operating lever (214) that has been usually done by a user or seat occupant, it is inevitable that the user or seat occupant will be confused and uncomfortable with operation of the lever (214) because he or she will do the opposite of what have been done to raise and lower the seat. That is, when it is desired to raise the seat, the user will have to rotate the lever (214) downwardly as opposed to the upward rotation that has been normally required to raise the seat.
To solve such problem, a rotation conversion or switch-over mechanism may be used to change the reverse rotation direction into a normal rotation direction. But, it will result in a complicated structure of the whole seat lifter and ratchet-type lever mechanism, and increased number of parts required as well as undesired high costs involved therein.
In view of the above-stated drawbacks, it is therefor a primary purpose of the present invention to provide an improved ratchet-type lever mechanism which permits normal rotation of operating lever in usual way without confusion to actuate a seat lifter means which includes: a brake means having a shaft operatively connected therewith, the brake means being adapted to provide a braking action to upward and downward motions of the seat lifter means and being rotatable in one of a first direction and a second direction opposite to the first direction; and a transmission mechanism operatively connected between the brake means and the seat lifter means, the transmission mechanism requiring a reverse rotation of the operating lever to cause the upward and downward motions of the seat lifter means in contrast to normal first and second rotations of the operating lever, wherein rotation of the shaft of brake means in said first direction is converted via the transmission mechanism into the downward motion of seat lifter means, and whereas rotation of the shaft of brake means in the second direction is converted via the transmission mechanism into the upward motion of seat lifter means,
In order to achieve such purpose, a ratchet-type lever mechanism in accordance with the present invention is basically comprised of:
a first ratchet gear wheel means rotatably provided about the shaft of brake means, which is so designed to be rotatable together with the shaft of brake means only when the shaft of brake means is rotated in the first direction;
a second ratchet gear wheel means rotatably provided about the shaft of brake means, which is so designed to be rotatable together with the shaft of brake means only when the shaft of brake means is rotated in the second direction;
a shaft means rotatably disposed in a spaced-apart relation with the shaft of brake means; the shaft means being connected with the operating lever such that a center of rotation of the operating lever is at a central axis of the shaft means; and
a ratchet gear means operatively provided between the shaft means and the first and second ratchet gear wheel means, the ratchet gear means including;
a sector gear means for transforming the reverse rotation of the operating lever required by the transmission mechanism into one of such normal first and second rotations of the operating lever, to thereby cause the shaft of the brake means to rotate in same direction as one of the normal first and second rotations of the operating lever, so that the normal first rotation of the operating lever causes the shaft of the brake means to rotate in the first direction, whereas the normal second rotation of the operating lever causes the shaft of the brake means to rotate in the second direction,
the sector gear means having, defined circumferentially thereof, a first arcuate gear means and a second arcuate gear means in such a manner that the first arcuate gear means is defined in an offset relation with the second arcuate gear means with respect to a center of the ratchet gear means, with such an arrangement that, when the operating lever is positioned in a non-use position, the ratchet gear means is normally positioned in a neutral point where the first and second arcuate arcuate gear means are out of engagement with the first and second ratchet gear wheel means, respectively, and that, when the first rotation of the operating lever is effected from the non-use position to cause the upward motion of the seat lifter means, the ratchet gear means is rotated to bring the first arcuate gear means to meshed engagement with the first ratchet gear wheel means, whereas, when the second rotation of operating lever is effected to cause the downward motion of seat lifter means, the ratchet gear means is rotated to bring the second arcuate gear means to meshed engagement with the second ratchet gear wheel means,
wherein the first rotation of said operating lever from the non-use position brings the first arcuate gear teeth to meshed engagement with the first ratchet gear wheel means, thereby causing rotation of the shaft of brake means in the first direction so as to cause the upward motion of the seat lifter means via the transmission mechanism, whereas the second rotation of operating lever from the non-use position brings the second arcuate gear teeth to meshed engagement with the second ratchet gear wheel means, thereby causing rotation of the shaft of brake means in the second direction so as to cause the downward motion of seat lifter means via the transmission mechanism.
Accordingly, a user can usually rotate the operating lever from the non-use position in one direction (e.g. in upward direction) to cause the upward motion of seat lifter means, and can also usually rotate the operating lever in another direction (e.g. in downward direction) from the non-use position to cause the downward motion of seat lifter means. In one aspect of the present invention, the first and second arcuate gear means may comprise a first outwardly-toothed sector gear teeth and a second outwardly-toothed sector gear teeth, respectively, and the sector gear means may comprise an outwardly toothed sector ratchet gear element including: a shaft disposed between the shaft means and the shaft of brake means; and a first outwardly-toothed sector gear element having, defined therein, a first outwardly-toothed sector gear portion and the first and second outwardly-toothed sector gear teeth in an integral manner; wherein the first outwardly-toothed sector gear element is rotatably provided on the shaft in such a manner that the first outwardly-toothed sector gear portion is disposed in a diametrically opposed relation with the first and second arcuate gear teeth with respect to the shaft; and a second outwardly-toothed sector gear element including a second sector gear portion formed therein, the second outwardly-toothed sector gear element being fixedly provided on the shaft means associated with the operating lever, wherein the second outwardly-toothed sector gear portion is in a meshed engagement with the first outwardly-toothed sector gear portion.
In another aspect of the present invention, the first and second arcuate gear means may comprise a first inwardly-toothed sector gear teeth and a second inwardly-toothed sector gear teeth, respectively. Also, the sector gear means may comprise an inwardly toothed sector ratchet gear element having a sectorial ring body in which the first and second inwardly-toothed sector gear teeth are formed, wherein the inwardly toothed sector ratchet gear element has: a connection end portion with which the operating lever is connected; and a securing portion defined between said sectorial ring body and the connection end portion, with the securing portion being fixedly connected with the shaft means.